The invention concerns an apparatus for the contactless detection of characteristics of continuously conveyed, translucent products, comprising firstly a transmitting unit having a light source for generating high-intensity light radiation, a light-converting element for forming a planar light field from the light radiation and a focusing element for forming a line of light running transversely to the direction of conveying F of the products from the planar light field, and secondly a receiving unit having a detection device for picking up the light radiation transflected by the product, wherein a shading element is arranged between the transmitting unit and the receiving unit.
Furthermore the invention concerns a method for the contactless detection of characteristics of continuously conveyed, translucent products, comprising the steps of: continuously conveying the products through an inspection region of a receiving unit, exposing the products to light radiation by a transmitting unit, and picking up the light radiation transflected by the products by the receiving unit.
Such apparatuses and methods are used in different industrial fields in which products are tested for certain characteristics. Possible characteristics are different product-specific properties, but also anomalies or foreign bodies and the like. In the fish-processing industry e.g. the detection of parasites inside fish fillets is of particular importance. This means that each fish fillet is tested for parasites, which are usually very small objects compared with the fish fillet. In this case the fish fillets are conveyed continuously at a very high speed of e.g. 40 cm/s or more on a transport element through an inspection region of a detection means.
It is known that the products, hence the fish fillets in the case of this example, can be exposed to light radiation. The light radiation which is scattered and/or reflected inside the translucent product is detected via the detection device and evaluated. To put it another way, the light radiation penetrates the products, wherein the light radiation is scattered without direction or reflected directionally inside the product, e.g. on foreign bodies. In addition further processes such as e.g. absorption and fluorescence may alter the spectral characteristic of the light as well. This light radiation obtained as a result of transflection (transflectance/interactance) (scattered and/or directed) is hereinafter also referred to as transflected light. The transflected light is then detected by the detection device. Known apparatuses are constructed so that they have a transmitting unit with a light source, wherein the light source beams high-intensity light radiation to a light-converting element. Within the light-converting element, in which e.g. glass fibre bundles can be arranged, the light radiation is shaped and conducted from the light input opening to the light output opening. The light-converting element has a planar opening in the output region for the light radiation. For physical reasons the light radiation scatters on leaving the light-converting element. This scattered light then encounters the focusing element which is arranged beneath the light-converting element and which focuses the planar light field to a line of light which runs transversely to the direction of conveying F of the products. In the known apparatuses, the transmitting unit is arranged either in front of the receiving unit or behind the receiving unit in the direction of conveying F of the products.
The problem with the existing apparatuses lies in that the single transmitting unit and hence the single light source on the one hand has too low a light intensity to illuminate/transilluminate the products sufficiently at high speeds of conveying, and on the other hand illuminates only a limited region of the fish fillet. This leads in particular to parts of the fish fillet, namely either in the leading region or in the trailing region, not being illuminated, as a result of which a full inspection is impossible.